Engineering Phonon, Photon, Electron and Plasmon interactions in Silicon - Metal Nanocavitiies for Silicon Photonics and Thermoplasmonics

ENGINEERING PHONON, PHOTON, ELECTRON AND PLASMON INTERACTIONS IN SILICON - METAL NANOCAVITIIES FOR SILICON PHOTONICS AND THERMOPLASMONICS Daksh Agarwal Ritesh Agarwal, PhD Silicon photonics offers a cost effective solution to achieve ultrafast data processing speeds. But due to its indirect bandgap structure, making lasers from silicon is extremely difficult. Thus research has focused on nonlinear Raman processes in silicon as a method to achieve optical gain. Silicon nanowires provide an interesting platform for enhancing these nonlinearities because of their small size, geometry and relevant length scales. In the current work Raman measurements done on silicon nanowires reveal that up to twelvefold enhancement in Stokes scattering intensity and fourfold enhancement in anti Stokes scattering intensity can be attained depending on cavity structure and size, and excitation wavelength. In some cavities Stokes intensity depends on the sixth power of pump intensity, indicating extreme nonlinearity. Numerical calculations, done to understand the mechanism of these results indicate that silicon nanowires confine light to highly intense electric field modes inside the cavity which lead to stimulated Stokes and anti Stokes Raman scattering. Cavity modes can also be tuned to enhance the relative emission of either one of anti Stokes or Stokes photons which could enhance cavity cooling. These results would enable the development of smallest monolithically integratable silicon laser with extremely low lasing threshold and could lead to the development of next generation of high speed and energy efficient processors. The intense electric field inside the nanowire could also be used to enhance the degree of plasmon excitation in metallic nanoparticles. Silicon nanowires coated with a 10 nm thick gold film lead to strong plasmon excitation in gold and high cavity absorption which enable the cavity to heat up to temperatures of 1000K at relatively low pump powers. The cavities also give the ability to measure temperature attained during plasmon excitation and control the plasmon resonance wavelength. Because of the strong heating and plasmonic effects, these cavities show enhanced evolution rates of hydrogen, a crucial industrial building block and a promising fuel, in photoreforming reactions of alcohols

Latest Expansions in Lipid Enhancement of Microalgae for Biodiesel Production: An Update

Research progress on sustainable and renewable biofuel has gained motion over the years, not just due to the rapid reduction of dwindling fossil fuel supplies but also due to environmental and potential energy security issues as well. Intense interest in microalgae (photosynthetic microbes) as a promising feedstock for third-generation biofuels has grown over recent years. Fuels derived from algae are now considered sustainable biofuels that are promising, renewable, and clean. Therefore, selecting the robust species of microalgae with substantial features for quality biodiesel production is the first step in the way of biofuel production. A contemporary investigation is more focused on several strategies and techniques to achieve higher biomass and triglycerides in microalgae. The improvement in lipid enhancement in microalgae species by genetic manipulation approaches, such as metabolic or genetic alteration, and the use of nanotechnology are the most recent ways of improving the production of biomass and lipids. Hence, the current review collects up-to-date approaches for microalgae lipid increase and biodiesel generation. The strategies for high biomass and high lipid yield are discussed. Additionally, various pretreatment procedures that may aid in lipid harvesting efficiency and improve lipid recovery rate are described

Engineering phonon, photon, electron and plasmon interactions in silicon-metal nanocavitiies for silicon photonics and thermoplasmonics

Silicon photonics offers a cost effective solution to achieve ultrafast data processing speeds. But due to its indirect bandgap structure, making lasers from silicon is extremely difficult. Thus research has focused on nonlinear Raman processes in silicon as a method to achieve optical gain. Silicon nanowires provide an interesting platform for enhancing these nonlinearities because of their small size, geometry and relevant length scales. In the current work Raman measurements done on silicon nanowires reveal that up to twelvefold enhancement in Stokes scattering intensity and fourfold enhancement in anti Stokes scattering intensity can be attained depending on cavity structure and size, and excitation wavelength. In some cavities Stokes intensity depends on the sixth power of pump intensity, indicating extreme nonlinearity. Numerical calculations, done to understand the mechanism of these results indicate that silicon nanowires confine light to highly intense electric field modes inside the cavity which lead to stimulated Stokes and anti Stokes Raman scattering. Cavity modes can also be tuned to enhance the relative emission of either one of anti Stokes or Stokes photons which could enhance cavity cooling. These results would enable the development of smallest monolithically integratable silicon laser with extremely low lasing threshold and could lead to the development of next generation of high speed and energy efficient processors. The intense electric field inside the nanowire could also be used to enhance the degree of plasmon excitation in metallic nanoparticles. Silicon nanowires coated with a 10 nm thick gold film lead to strong plasmon excitation in gold and high cavity absorption which enable the cavity to heat up to temperatures of 1000K at relatively low pump powers. The cavities also give the ability to measure temperature attained during plasmon excitation and control the plasmon resonance wavelength. Because of the strong heating and plasmonic effects, these cavities show enhanced evolution rates of hydrogen, a crucial industrial building block and a promising fuel, in photoreforming reactions of alcohols

Towards a validated patient-specific computational modeling framework to identify failure regions in traditional growing rods in patients with early onset scoliosis

Background: While growing rods are an important contribution to early-onset scoliosis treatment, rod fractures are a common complication that require reoperations. A recent retrieval analysis study performed on failed traditional growing rods revealed that there are commonalities among patient characteristics based on the location of rod fracture. However, it remains unknown if these locations correspond to high stress regions in the implanted construct. Methods: A patient-specific finite element scoliotic model was developed to match the pre-operative (pre-op) scoliotic curve of a patient as described in previously published articles, and by using the patient registry information along with biplanar radiographs. A dual stainless-steel traditional growing rod construct was implanted into this scoliotic model and the surgical procedure was simulated to match the post-operative (post-op) scoliotic curve parameters. Muscle stabilization and gravity was simulated through follower load application. Rod distraction magnitudes were chosen based on pre-op to post-op cobb angle correction, and flexion bending load was simulated to identify the high stress regions on the rods. Results: The patient-specific finite element model identified two high stress regions on the posterior surface of the rods, one at mid construct and the other adjacent to the distal anchors. This correlated well with the data obtained from the retrieval analysis performed by researchers at U.S. Food and Drug Administration (FDA) which showed the posterior surface of the rod as the fracture initiation site, and the three locations of failure as mid-construct, adjacent to distal anchors, and adjacent to tandem connector. Conclusions: The result of this study confirms that the high stress regions on the growing rods, as identified by the FEA, match the fracture prone sites identified in the retrieval analysis performed at the FDA. This proof-of-concept patient-specific approach can be used to predict sites prone to fracture in growing rods

Engineering Localized Surface Plasmon Interactions in Gold by Silicon Nanowire for Enhanced Heating and Photocatalysis

The field of plasmonics has attracted considerable attention in recent years because of potential applications in various fields such as nanophotonics, photovoltaics, energy conversion, catalysis, and therapeutics. It is becoming increasing clear that intrinsic high losses associated with plasmons can be utilized to create new device concepts to harvest the generated heat. It is therefore important to design cavities, which can harvest optical excitations efficiently to generate heat. We report a highly engineered nanowire cavity, which utilizes a high dielectric silicon core with a thin plasmonic film (Au) to create an effective metallic cavity to strongly confine light, which when coupled with localized surface plasmons in the nanoparticles of the thin metal film produces exceptionally high temperatures upon laser irradiation. Raman spectroscopy of the silicon core enables precise measurements of the cavity temperature, which can reach values as high as 1000 K. The same Si–Au cavity with enhanced plasmonic activity when coupled with TiO₂ nanorods increases the hydrogen production rate by ∼40% compared to similar Au–TiO₂ system without Si core, in ethanol photoreforming reactions. These highly engineered thermoplasmonic devices, which integrate three different cavity concepts (high refractive index core, metallo-dielectric cavity, and localized surface plasmons) along with the ease of fabrication demonstrate a possible pathway for designing optimized plasmonic devices with applications in energy conversion and catalysis

Synthesis and Characterization of Highly Crystalline Bi-Functional Mn-Doped Zn2SiO4 Nanostructures by Low-Cost Sol–Gel Process

Herein, we demonstrate a process for the synthesis of a highly crystalline bi-functional manganese (Mn)-doped zinc silicate (Zn2SiO4) nanostructures using a low-cost sol–gel route followed by solid state reaction method. Structural and morphological characterizations of Mn-doped Zn2SiO4 with variable doping concentration of 0.03, 0.05, 0.1, 0.2, 0.5, 1.0, and 2.0 wt% were investigated by using X-ray diffraction and high-resolution transmission electron microscopy (HR-TEM) techniques. HR-TEM-assisted elemental mapping of the as-grown sample was conducted to confirm the presence of Mn in Zn2SiO4. Photoluminescence (PL) spectra indicated that the Mn-doped Zn2SiO4 nanostructures exhibited strong green emission at 521 nm under 259 nm excitation wavelengths. It was observed that PL intensity increased with the increase of Mn-doping concentration in Zn2SiO4 nanostructures, with no change in emission peak position. Furthermore, magnetism in doped Zn2SiO4 nanostructures was probed by static DC magnetization measurement. The observed photoluminescence and magnetic properties in Mn-doped Zn2SiO4 nanostructures are discussed in terms of structural defect/lattice strain caused by Mn doping and the Jahn–Teller effect. These bi-functional properties of as-synthesized Zn2SiO4 nanostructures provide a new platform for their potential applications towards magneto-optical and spintronic and devices areas